Development and Testing of a Span-Extending Morphing Wing

Abstract

Recent developments in morphing aircraft research have motivated investigation into conformal morphing systems, that is, shape change without discrete moving parts or abrupt changes in the airfoil profile. In this study, implementation of a continuous span morphing wing is described. The system consists of two primary components: (1) zero-Poisson ratio morphing core and (2) fiber-reinforced elastomeric matrix composite skin with a nearly zero-Poisson ratio in-plane. The main goal for improved air vehicle efficiency was a nominal 100% change in area of the active wing section with less than 2.54 mm out-of-plane deflection under representative aerodynamic loading. Objectives of this study included exploring fabrication techniques for advanced morphing core shapes (i.e., having airfoil-shaped cross-section), exploiting customizable design parameters of in-house fabricated skin and core material, designing a prototype wing structure such that integration with a candidate UAV was feasible, and experimentally evaluating a laboratory prototype. As a result of this study, the ability to physically build and test a viable airfoil structure capable of increasing its planform area by 100% (doubling span with constant chord) was demonstrated on a prototype hardware demonstration article. Satisfying objectives of designing, fabricating, and testing a prototype morphing wing section capable of 100% span extension, while maintaining constant chord, a wind tunnel test highlighted the resulting viable aerodynamic surface in a wind tunnel test up to 130 km/h wind speeds. The prototype wing in its resting condition had a span of 61.0 cm, which could be extended to 122.0 cm, with less than 2.54 mm out-of-plane deflection in dynamic pressures consistent with the maximum speed, 130 km/h, of a candidate unmanned aerial vehicle platform. In meeting these goals, the morphing core was successfully transitioned from a simple 1D concept into a complex, cambered airfoil with sufficient free volume to house an actuation system. A refined elastomer matrix composite skin fabrication technique was also devised and experimentally validated on skins of various thicknesses and overall dimensions.